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Old 11-09-2017, 10:46   #1
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GPS "Dead" Zones?

Hi folks,
I just returned from my first trip to the Isthmus at Catalina, which was great. On the way there my Garmin GPS suddenly lost all satellite contact. It lasted for maybe 15 minutes before coming back online. During that time I checked all connections at the display and antennae, but could find no reason for it. Yesterday, on the way home, I lost satellite contact again in the exact same spot, which is off of Pt. Mugu, where there are heavy military coms. This time it only lasted about a minute or two.

It seems like if it was a bad electrical connection it might do this, with the exception of losing contact in the exact same geographical spot. So, have any of you encountered GPS "Dead" spots before? All comments and opinions are welcomed.

Cheers, Bill
M/V Ansedonia
'91 Californian 52 CPMY
Lying La Paz, BCS, Mexico
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Old 11-09-2017, 11:31   #2
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Re: GPS "Dead" Zones?

There was a FAA notice in June (IIRC) that GPS may be less than reliable in the southwest. Navy testing something.

To know if it's your equipment - use more than one GPS. Your phone is an excellent backup GPS.
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Old 11-09-2017, 12:45   #3
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Re: GPS "Dead" Zones?

Had a similar issue in the Channel Islands. Turned out that my solar panels blocked the built-in antenna on my helm-mounted chart plotter. In my case, simply (temporarily) moving the CP to a spot where the antenna had a good signal was sufficient. Once synched with the satellites, the unit worked fine in its normal position.

I've had a similar problem on rare occasions when the plotter has been powered down for a considerable time, so it takes a long time to find enough satellites for a fix. Again, giving the antenna an unobstructed view helped a lot.
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Old 11-09-2017, 16:22   #4
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Re: GPS "Dead" Zones?

There have been some very big solar flares lately, which can interfere with GPS signals. But I don't think they exactly align with the time/date you had trouble. . . .
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Old 11-09-2017, 17:18   #5
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Re: GPS "Dead" Zones?

I have had accuracy issues with gps. I have left the nav programs on at anchor and at my home dock. The tracks generated cover as much as 200 yards. Track is always moving. Sometimes it takes off in a line even further. Much more than the anchor chain and the dock is fixed by pilings. I use TZ Navigator and OpenCPN and have Furuno GPS, a puck gps and a reciever for the European and Russian systems that also reads gps. They all do it. The Euro/Russian is a little worse. I suppose in Alaska, the mountains eliminate some of the satellites. Still much better than Loran or stars on the ocean. Pic is at a dock, open sky.
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Old 11-09-2017, 18:10   #6
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Re: GPS "Dead" Zones?

I think it's signal quality or the lack of it anyway.
Usually there is a page where you can view the Sats your tracking and the DOP or EPE, dilution of precision, or estimated position error.

I gave up on Drag Queen as a phone app even though it's great, but my phone would suddenly travel a ways in the middle of the night and set the alarm off, but by the time I got up and checked it, it was accurate again, took a few times for me to figure out what was going on
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